Stigmatomma oregonense

Quick Summary

• Difficulty: Expert
• Origin & Habitat: Pacific Northwest of North America, from southern British Columbia through northern California. Found in shaded, mixed coniferous forest dominated by Douglas fir, pine, incense cedar, and fir, along with maple and oak. Elevation ranges from 580 to 1740 m. Nests under bark of large, moist, rotten coniferous logs in forest ^[1][2].
• Colony Type: Polygynous, colonies contain multiple queens and are often spread diffusely through a log. Field studies have found populous multiple-queen colonies with abundant brood ^[1].
• Size & Growth:
  • Queen: Similar to workers but with larger eyes, dealated queens are known ^[1].
  • Worker: Large for the genus, total length not given in available research ^[1].
  • Colony: Colonies can be populous with abundant brood ^[1].
  • Growth: Moderate, laboratory colonies showed slow decline with high larval mortality ^[1].
  • Development: Unknown, specific timeline not documented. Based on typical Amblyoponinae patterns, you might expect 8-12 weeks at optimal temperature. (Lab colonies in California produced alates between August 6-14 from a July collection, suggesting several months for sexual brood development ^[1].)
• Antkeeping:
  • Temperature: Keep cool to moderate (18-22°C). These ants inhabit shaded forest at higher elevations (580-1740 m), so avoid warm conditions. Room temperature is likely fine, but monitor with a thermometer ^[1].
  • Humidity: High humidity is essential. They nest in moist, rotten logs in shaded forest. Keep the nest substrate consistently damp but not waterlogged. Provide a moisture gradient so ants can choose their preferred zone ^[1].
  • Diapause: Likely yes, as a temperate species from higher elevations, they probably need a winter rest period. Alates emerge in August-September, hinting at a seasonal cycle. Provide 3-4 months at 10-15°C (roughly November through February). Keep substrate slightly less moist but not dry.
  • Nesting: Under bark of large, moist, rotten coniferous logs in nature ^[1]. In captivity, use a naturalistic setup with rotten wood or cork bark, plus dark, tight chambers. Y-tong or plaster nests can work if kept moist.
• Behavior: Workers are centipede specialists. They sting prey repeatedly, drag it to the nest, then spend 1-3 hours chewing and liquefying it. During that time they drink hemolymph from the prey. Larvae are piled onto the centipede to feed. Queens and workers also practice non‑lethal cannibalism, puncturing larvae to feed on hemolymph, this behavior increases when centipedes run out ^[1]. They have a functional sting (typical of Amblyoponinae) but are not aggressive toward keepers. Escape risk is moderate: they can climb smooth surfaces but aren't extreme escape artists.
• Common Issues: specialized diet, they refuse most standard feeder insects and need live geophilomorph centipedes., laboratory colonies consistently decline with high larval mortality, long‑term maintenance may be very difficult., high humidity requirements can cause mold if ventilation is poor., non‑lethal cannibalism means larvae may get damaged if prey runs out., polygynous structure may complicate colony establishment compared to single‑queen species.

Housing and Nest Setup

Stigmatomma oregonense needs a naturalistic setup that mimics rotten logs. The best approach is a terrarium with several inches of moist soil and rotting wood fragments, topped with pieces of cork bark or actual rotten wood. Keep the setup consistently damp but not waterlogged, these ants come from damp forest floors. A small water reservoir or regular misting helps. Provide darkness for the nest area, they prefer dark, enclosed spaces under bark. Because colonies are polygynous and spread out, give them room to distribute brood across multiple chambers ^[1].

Feeding and Diet - The Critical Challenge

This is the hardest part of keeping S. oregonense. They are extreme centipede specialists, geophilomorph centipedes (the long, flexible kind) are their main wild prey ^[1]. Lab colonies readily accepted those but showed little interest in lithobiomorph centipedes (the short, common kind). They also ate small arthropods like Drosophila but couldn't be sustained long‑term on them. You'll need to provide live geophilomorph centipedes regularly, collected from moist soil or bought from specialists. When workers catch one, they sting it repeatedly, drag it to a brood chamber, and chew it for 1-3 hours before larvae feed. Workers also drink hemolymph oozing from the prey ^[1].

Temperature and Seasonal Care

Keep S. oregonense cool to moderate. Their natural habitat is shaded coniferous forest at 580-1740 m, where temperatures stay relatively cool. Aim for 18-22°C in the nest. Avoid warm conditions, overheating likely contributed to colony decline in labs. For seasonal care, provide a winter diapause: alates emerge in August-September, suggesting a seasonal cycle. From November through February, reduce temperature to 10-15°C and cut back feeding. Keep the substrate slightly less moist during hibernation but don't let it dry out fully. Return to normal temps gradually in spring ^[1].

Colony Structure and Social Behavior

S. oregonense is polygynous, colonies naturally contain multiple cooperating queens. Field collections found multiple‑queen colonies with abundant brood under bark of large, moist, rotten logs ^[1]. An unusual behavior documented in captivity is non‑lethal cannibalism: when prey runs low, queens and workers puncture larvae to feed on their hemolymph. Larvae get scars but survive. This behavior increases when centipedes are scarce ^[1]. Workers also lick the surface and cuts of centipedes, drinking hemolymph. This social structure means colony fragments can establish more easily since several queens may be present.

Reproduction and Nuptial Flights

Alates (winged queens and males) emerge in late summer. Lab colonies produced alates between August 6-14 from a July collection. Field‑collected alates from California and Oregon span August 22 to September 18 ^[1]. One record from Oregon notes a swarm at 4 p.m. before rain, suggesting afternoon flights possibly triggered by weather changes. If you maintain a colony long‑term, expect sexual brood to develop in summer, with alates emerging in late August or September. The exact founding method of new queens (claustral or semi‑claustral) has not been documented.

Frequently Asked Questions

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References